The present invention relates to an apparatus for melting ash, particularly to an extremely efficient and downsizable apparatus which is directed to detoxifying and reusing ash to be left after incineration of industrial waste, and which melts ash to convert it into the form of granule, block or fiber.
Today, dioxin, heavy metals, etc. contained in ash to be left as waste after incineration of domestic, industrial and hospital refuse and discarded in the environment are giving rise to serious social problems, and means for treating them have been sought for.
There have recently been disclosed methods as means for treating such ash waste, which carry out melting and solidification of ash to achieve weight reduction and detoxification thereof. For example, Japanese Unexamined Patent Publication No. Hei 05-261358 discloses a method in which melting of ash is carried out by means of arc melting and resistance melting.
The above method involve problems that, while the furnace is heated to a high temperature of 2,000xc2x0 C. or higher and it is difficult to carry out temperature control, there is substantially no furnace material which can withstand such temperatures, and in order to cope with the high temperatures, the thickness of furnace materials is increased, leading to increase in size of the furnace; and that since the furnace body undergoes wearing heavily and since there is taken no countermeasure for it, the furnace body needs wholesale servicing under long-term interruption of operation of the apparatus in a short cycle, leading to extremely low production efficiency and increase in maintenance cost of equipment.
Meanwhile, for example, Japanese Unexamined Patent Publication Nos. Hei 10-220964, 2000-039267 and 2000-097425 each disclose an ash melting apparatus utilizing a phenomenon of the generally so-called thermit reaction to be induced by heating a mixture of a metal oxide and an aluminum powder to generate a large quantity of heat by oxidation of aluminum. However, the apparatus likewise involves the problems as described above, since it is difficult here again to carry out temperature control, and since the apparatus is frequently heated to a temperature of 2,000xc2x0 C. or higher.
Meanwhile, Japanese Unexamined Patent Publication No. Hei 8-226622, which is directed to providing an inexpensive and small-sized ash melting apparatus, containing a furnace body having an exhaust port, a mechanism of feeding ash into the furnace body and a burner for burning a heavy oil in the furnace body, discloses a constitution in which the furnace body contains means for supplying a gas which increases susceptibility of a fuel to burn, and the exhaust port is of such a size as will increase the internal pressure of the furnace body.
Since the main purpose of the above method is to use heavy oil as a fuel, use of the fuel having a large number of carbon atoms requires a large quantity of air necessary for achieving complete combustion thereof, and the air cools the furnace to prevent the internal temperature of the furnace from rising to a sufficient level. Therefore, ventilation is regulated to provide an increased pressure in the furnace so as to reduce cooling and to attain the predetermined temperature. However, the insufficient ventilation makes it difficult to maintain well the state of complete combustion, bringing about problems including insufficient temperature, abnormal combustion, noxious gas formation and scattering of ash.
In view of the problems described above, the present invention is directed to attaining easily a target temperature of 1,600 to 1650xc2x0 C. without increasing the internal temperature of the furnace; to increase durability of the furnace body by reducing wastage thereof due to ease of temperature control and to absence of abnormal temperature rise to 2,000xc2x0 C. or higher; to further extend the periodical servicing cycle of the furnace by using a less-wearing material in a zone of the innermost layer of the furnace containing a plurality of layers to be brought into contact with a high-temperature molten ash; and to make the furnace body of the innermost layer into a form of cartridge to enable easy replacement thereof, thus reducing out-of-production period for troubleshooting of the furnace body, improving production efficiency by a wide margin and enabling downsizing of the furnace body.
In the present invention, in order to attain the subjects described above, the following measures were taken: wearing of the furnace body is reduced by using a less-wearing crucible as the innermost layer of the furnace body and by facilitating temperature control so as to avoid abnormal temperature rise; the crucible is allowed to have the form of cartridge so as to fully facilitate replacement thereof; an oil having a small number of carbon atoms such as propane and butane is used mainly as a fuel, which is subjected to complete combustion in the presence of a relatively small amount (approximately equivalent amount) of oxygen gas or air supplied at a relatively low flow rate during combustion in well-ventilated normal conditions without regulation of ventilation for pressurization, so as to fully attain necessary temperatures; and means is employed for arranging a burner equipped substantially at the center of a cover which is provided at a side position, an ash charge port, a discharge port located at a lower position, etc. in position so as to improve heat efficiency. By equipping the burner at the center of the cover which is provided at a side position, burning gas dashes into the crucible and does not dash out from the discharge port.